Understanding Food Chapter 11: Milk

Composition of Milk The basic composition of milk regardless of the source remains the same: Water 87.3% Carbohydrate 4.8% Protein 3.4% Fat 3.7% Minerals 0.8%

Composition of Milk Casein: The primary protein (80%) found in milk; it can be precipitated (solidified out of solution) with acid or certain enzymes. Whey: The liquid portion of milk, consisting primarily of 93% water, lactose, and whey proteins (primarily lactalbumin and lactoglobulin).

Purchasing Milk Milk is graded according to its bacterial count. The law requires that all Grade A milk and milk products crossing state lines must be pasteurized. Grading is voluntary and is paid for by the dairy industry.

Purchasing Milk Ultrapasteurization: A process in which a milk product is heated at or above 280°F (138°C) for at least two seconds. Ultrahigh-temperature (UHT) Milk: Milk that has been pasteurized using very high temperatures, is aseptically sealed, and is capable of being stored unrefrigerated for up to three months.

Purchasing Milk Homogenization: A mechanical process that breaks up the fat globules in milk into much smaller globules that do not clump together and are permanently dispersed in a very fine emulsion.

Types of Milk About half the milk produced in the United States is sold as fluid milk and cream. Imitation milk: A product defined by the FDA as having the appearance, taste, and function of its original counterpart but as being nutritionally inferior.

Types of Milk Evaporated milk Sweetened condensed milk 60% of water evaporated sterilized Sweetened condensed milk 50% of water evaporated 40-45% sugar by weight Sterilzation not needed

Types of Milk Cultured or fermented milk products have been used for centuries. Some cultured milk products commonly consumed in North America are: Buttermilk Yogurt Acidophilus milk

Types of Milk Probiotics: Live microbial food ingredients (i.e., bacteria) that have a beneficial effect on human health. Prebiotics: Nondigestible food ingredients (generally fibers such as fructooligosaccharides (FOS) and inulin) that support the growth of probiotics.

Milk Products in Food Preparation Flavor Changes The bland, slightly sweet flavor of milk comes from its lactose, salts, sulfur compounds, and short-chain fatty acids. The percentage of fat determines the mouthfeel and body of a particular milk. Exposure to heat or sunlight, oxidation, the use of copper equipment or utensils, and the feed ingested by the source animal are just some of the other factors that can influence the flavor of milk.

Milk Products in Food Preparation Coagulation and precipitation Scorching Skin formation Acid Curdling

Milk Products in Food Preparation Some milk proteins coagulate or precipitate to form a solid clot, or curd, under certain conditions. These conditions include: Application of heat Addition of: Acid Enzymes Polyphenolic compounds Salts

Milk Products in Food Preparation Adding acid to milk causes the casein in the milk to coagulate. Milk also coagulates and forms curds when it is combined with certain enzymes originating from animal, plant, or microbial sources. Rennin: An enzyme obtained from the inner lining of a calf ’s stomach and sold commercially as rennet.

Milk Products in Food Preparation Whipped Milk Products During whipping, the protein in these milk products is mechanically stretched into thin layers that trap air bubbles, fat particles, and liquid.

Milk Products in Food Preparation

Storage of Milk Products Refrigerated All fluid milk except unopened, aseptic packs of ultrahigh-temperature pasteurized milk and certain canned milk products should be stored in the refrigerator.

Storage of Milk Products Dry Storage Nonfat dry milk stored away from moisture and in tightly closed containers will keep for about one year. Unopened cans of evaporated and sweetened condensed milks will keep up to a year in dry, ventilated areas, double that if refrigerated. Ultrapasteurized milk can be stored unopened at room temperature for up to three months. They should all be stored at or slightly below room temperature (72°F/22°C). Once opened, all these milks must be refrigerated.